496 CUVIER'S CHINCHILLA CHAP. to a separate family which will include but the one species, D, 'branickii. Fam, 6. CMacMllidae.—This family, likewise South American, contains three genera,1 all of which agree in having long limbs, especially the hind-limbs, and a bushy and well-developed tail. The hair is exceedingly soft, hence the commercial value of "' chinchilla." The genus Chinchilla,, containing but a single species, C. lani- ger, is a small and squirrel-like creature, living at considerable heights in the Andes. The eyes, as it is a nocturnal creature, are naturally large; and so also are the ears. The fore-feet have five toes, the hind-feet only four; they are furnished with feeble nails. The innermost toe of the hind-foot has a flat and nail-like claw. There are thirteen dorsal vertebrae, and the long tail has more than twenty. The clavicle is well developed, as in the other genera of this family. The large intestine of this animal is extraordinarily long; the proportions of the different regions of the gut are shown by the following measurements: small intestine, 820 mm.; caecum, 125 mm.; large intestine, 1340 mm. Such a disproportion between the large intestine and the small, to the advantage of the former, is a very strange fact in the anatomy of this Rodent. The genus Lagidium (also called Lagotis), which includes " Cuvier's Chinchilla/* is also a mountain dweller. There are several species of this genus, which differs from Chinchilla by the complete abortion of the thumb and of the great toe. The intestinal proportions are those of Chinchilla. The ears and tail are long. L. cumeri measures 1-|- feet in length. Lagostomus, again, has but one species, L. trichodactylus. The animal has a tail about half the length of the body. The digits are reduced as compared with Chinchilla, there being but four on the fore- and three on the hind-feet. There are only twelve dorsal vertebrae, and seven ribs reach the sternum. In the skull a dis- tinguishing mark from the last two genera is the separation of the infra-orbital foramen into two by a thin lamella of bone. The large intestine is between one-half and one-third the length of the small intestine, and thus differs much from that of Chinchilla. 1 AJO. account of the three genera is to 6e found in Trans, Zool. Soc. i. 1833, p. 8&, hy Mr. E. T. Bennett.